The present invention relates to a fiber-reinforced rod segment and more specifically to fishing rods constructed of graphite fiber-reinforced resins.
For a number of years, rods, such as fishing rods, have been made from multiple plies of fibers which are wrapped about a mandrel to form a hollow rod. The plies normally use an epoxy or other suitable plastic resin to bond the fibers together. The multiple ply rod segment is normally cured on the mandrel and then removed to form the lightweight hollow fishing rod blank.
In order to achieve rods having reduced weight and increased strength, the prior art teaches several different arrangements of the fiber plies in order to achieve high strength. For example, in U.S. Pat. No. 2,749,643, a rod having an outer layer of longitudinally extending glass fiber is shown. That rod has an inner layer of helically wound glass fibers. The two layers are bonded by a flexible plastic resin. In the rod discussed in U.S. Pat. No. 2,749,643, the outer fibers are described as serving as tension and compression members to resist bending of the rod. The inner layer of helically wound fibers is described as resisting crushing to give the rod blank adequate hoop strength. The provision of adequate hoop strength is important to keep the spacing of the outer layers uniform from the neutral axis to obtain maximum bending resistance.
When tapered hollow rods were introduced using graphite filaments in the inner helically wound layer, the hoop and crush strength were provided by wound filaments. The outer plies are formed from a pattern sheet having a right triangular shape having parallel fibers which are aligned with the longitudinal edge of the pattern. When the outer ply is positioned with the short side of the triangle positioned at the large diameter end of the mandrel and the mandrel is rolled across the outer ply, the mandrel moves more rapidly across the outer ply than does the remainder of the mandrel so that the fibers at the large diameter end progressively increase their angle with respect to the axis of the mandrel as they approach the exterior of the rod. After the curing of the wrapped mandrel and consolidation of the plies into an integral laminate, the mandrel is removed and a flexible rod remains. This provides a rod which has a gradually reduced thickness of the outer layer as one moves toward the tip or smaller end of the rod. Although the rod which results is considerably lighter than the fiberglass reinforced rods shown in U.S. Pat. No. 2,749,643, the strength increase is apparently not significantly increased over those rods.
A further attempt to provide an improved rod having optimum bending characteristics and hoop strength is shown in U.S. Pat. No. 4,061,806 which indicates that improved performance can be obtained by utilizing an outer layer of bonded longitudinal glass fibers of less thickness than shown in U.S. Pat. No. 2,749,643 and an inner layer of helically wound graphite filaments impregnated with a resin bonding agent.